15. A family is comparing different car seats. One car seat is designed for a child up to and including 30 lb. Another car seat is designed for a child between
15 lb and 40 lb. A third car seat is designed for a child between 30 lb and 85 lb,
inclusive. Model those ranges with compound inequalities. Which car seats are
appropriate for a 32-Ib child?

Set $r$ is a set of rectangles such that (1) only the grid points shown here are used as vertices, (2) all sides are vertical or horizontal and (3) no two rectangles in the set are congruent. if $r$ contains the maximum possible number of rectangles given these conditions, what fraction of the rectangles in set $r$ are squares? express your answer as a common fraction.